This application relates to the art of attenuators and, more particularly, to attenuators for reducing the intensity of light signals in fiber optic cables. The invention is particularly applicable to attenuation of light signals having a wavelength of 1550xcexcm in fiber optic cable having a diameter of 900xcexcm and will be described with specific reference thereto. However, it will appreciated that the invention has broader aspects and can be used for other wavelengths of light as well as with fiber optic cables having other diameters.
Equipment that is designed to operate on a particular range of light input signals will not operate properly if the input is too high. By way of example, it may be desirable to have an input in the range of 0 to minus 4 dB from a fiber optic cable that actually is delivering plus 1 to minus 3 dB. Therefore, it is necessary to attenuate the signals from the fiber optic input cable to bring them down within the acceptable range.
Many arrangements for light attenuation in fiber optic cables have undesirable insertion losses due to splices, connectors or the manner in which attenuation is achieved, and many of these devices are inserted directly in the path of the signal requiring attenuation. It would be desirable to have an arrangement for incrementally attenuating light signals in fiber optic cables with no insertion losses and with very low polarization dependent losses.
A light signal attenuator for fiber optic cables in accordance with the present application provides attenuation up to at least 2 dB in at least five increments.
An attenuator in accordance with the present application has a generally rectangular base with opposite ends, opposite sides, and upper and lower surfaces. However, it will be appreciated that other shapes can be used. A pair of cable looping devices or spools extend upwardly from the upper surface of the base for looping a fiber optic cable therearound to obtain a desired attenuation.
In one arrangement, the spools are formed by a plurality of circumferentially-spaced arcuate arms extending upwardly from the upper surface of the base on the periphery of a circle. The spools have spool axes that lie on a common longitudinal axis that extends between the ends of the base and bisects the base between its sides.
A plurality of spaced-apart fiber optic cable guideways in the form of recesses open upwardly of the base in alignment with elongated grooves in the base upper surface adjacent the opposite sides thereof.
Hollow fastening and stacking bosses extend upwardly from the upper surface of the base adjacent the opposite ends thereof. Sockets in the underside of the base in alignment with the fastening and stacking bosses are provided for receiving upper end portions of the bosses on an adjacent tray to provide stackability.
It is a principal object of the present invention to provide an improved light attenuator for use with fiber optic cables.
It is an additional object of the invention to provide such an attenuator that has a pair of cable looping devices thereon.
It is a further object of the invention to provide such an attenuator having cable guideways for guiding a cable in a desired path to and from the looping devices.
It is another object of the invention to provide such an attenuator that is molded in one-piece of plastic material.
It is also an object of the invention to provide such an attenuator that is symmetrical so that either end may function as the entrance or exit end.